Rapamycin (Sirolimus) is a 31-member natural macrocyclic lactone [C51H79N1O13; MWt=914.2] produced by Streptomyces hygroscopicus and found in the 1970s (U.S. Pat. No. 3,929,992; U.S. Pat. No. 3,993,749). Rapamycin (structure shown below) was approved by the Food and Drug Administration (FDA) for the prophylaxis of renal transplant rejection in 1999.

Rapamycin resembles tacrolimus (binds to the same intracellular binding protein or immunophilin known as FKBP-12) but differs in its mechanism of action. Whereas tacrolimus and cyclosporine inhibit T-cell activation by blocking lymphokine (e.g., IL2) gene transcription, sirolimus inhibits T-cell activation and T lymphocyte proliferation by binding to mammalian target of rapamycin (mTOR). Rapamycin can act in synergy with cyclosporine or tacrolimus in suppressing the immune system.
Rapamycin is also useful in preventing or treating systemic lupus erythematosus [U.S. Pat. No. 5,078,999], pulmonary inflammation [U.S. Pat. No. 5,080,899], insulin dependent diabetes mellitus [U.S. Pat. No. 5,321,009], skin disorders, such as psoriasis [U.S. Pat. No. 5,286,730], bowel disorders [U.S. Pat. No. 5,286,731], smooth muscle cell proliferation and intimal thickening following vascular injury [U.S. Pat. Nos. 5,288,711 and 5,516,781], adult T-cell leukemia/lymphoma [European Patent Application 525,960 A1], ocular inflammation [U.S. Pat. No. 5,387,589], malignant carcinomas [U.S. Pat. No. 5,206,018], cardiac inflammatory disease [U.S. Pat. No. 5,496,832], anemia [U.S. Pat. No. 5,561,138] and increase neurite outgrowth [Parker, E. M. et al, Neuropharmacology 39, 1913-1919, 2000].
Although rapamycin can be used to treat various disease conditions, the utility of the compound as a pharmaceutical drug has been restricted by its very low and variable bioavailability and its high immunosuppressive potency and potential high toxicity. Also, rapamycin is only very slightly soluble in water. To overcome these problems, prodrugs and analogues of the compound have been synthesized. Water soluble prodrugs prepared by derivatizing rapamycin positions 31 and 42 (formerly positions 28 and 40) of the rapamycin structure to form glycinate, propionate, and pyrrolidino butyrate prodrugs have been described (U.S. Pat. No. 4,650,803). Some of the analogues of rapamycin described in the art include monoacyl and diacyl analogues (U.S. Pat. No. 4,316,885), acetal analogues (U.S. Pat. No. 5,151,413), silyl ethers (U.S. Pat. No. 5,120,842), hydroxyesters (U.S. Pat. No. 5,362,718), as well as alkyl, aryl, alkenyl, and alkynyl analogues (U.S. Pat. Nos. 5,665,772; 5,258,389; 6,384,046; WO 97/35575).
Prodrugs and analogues of rapamycin are synthesized by chemical synthesis, where additional synthetic steps are required to protect and deprotect certain positions. Analogues can also be synthesized biologically, where the Streptomyces strain is genetically modified to produce these analogues of rapamycin. The analogues need to maintain necessary positions for protein binding or other cellular interactions and not generate steric hindrance in order to preserve its activity. The safety of these analogues requires extensively testing by series of preclinical and clinical experimentations.
The present invention comprises novel macrocyclic lactones and novel uses for macrocyclic lactones, where the compositions can be synthesized chemically or biologically and which preserve at least some immunosuppressive, anti-proliferative, anti-fungal and anti-tumor properties for use in systemic and site specific applications.